Tocopherol compounds, also designated as vitamin E, are active components in vegetable oils. Vitamin E activity refers to the physiological activity of this group of nutrient materials. Materials having a vitamin E activity all belong to a distinct series of compounds which are all derivatives of chroman-6-ol. These compounds are all tocol derivatives having an isoprenoid C.sub.16 -sidechain. The term "tocol" is used to mean 2-methyl-2-(4',8,12'-trimethyltridecyl)chroman-6-ol. These compounds are alpha-, beta-, gamma-, and delta-tocopherol, and are of primary importance for vitamin E activity. Of these, alpha-tocopherol has the highest vitamin E activity and is the most valuable.
Such naturally occurring tocopherol homologues are generally isolated from natural products such as vegetable oil sources by various combinations of procedures such as esterification, saponification, extraction, distillation, ion exchange, adsorption chromotography, precitipation of sterols, and crystallization. The tocol concentrate isolated will vary depending on the particular separation technique used in addition to the vegetable source. One such concentrate, for example, contains mixtures of tocopherol with approximately 40% by weight residual sterols and hydrocarbons.
A well known commercial activity is the conversion of tocopherol, and especially d-alpha-tocopherol into a solid form for convenient human consumption. One of the best methods commercially used to solidify tocopherol is to prepare tocopherol succinate. Typically, tocopherol succinate is prepared by reacting tocopherol with succinic anhydride, and then isolating the half ester product by crystallization. References describing methods of this nature are described in U.S. Pat. No. 3,538,119 and in British Pat. No. 866,489. Another reference which describes both the preparation of alpha-tocopheryl succinate and its recovery is British Pat. No. 1,114,150.
For medicinal and health applications requiring tocopherol, solid tocopherol derivatives are prepared. It is desired that such tocopherol derivatives be capable of dissolving in an aqueous solution and be highly potent with a high degree of vitamin E biological activity per unit. The preparation of tocopherol derivatives is described in U.S. Pat. No. 2,680,749, which describes, as a preferred method, reacting tocopherol with a suitable polybasic acid anhydride such as succinic acid anhydride under usual esterification conditions. The tocopherol acid esters are then esterified with polyethylene glycol also in accordance with well known esterification techniques.
Vitamin E derivatives disclosed in the early disclosure No. 58-203982 for Application No. 57-87580, published by the Japanese Patent Bureau includes mono amino dicarboxylic acid derivatives of tocopherol. Such compounds, according to this reference are vitamin E derivatives formed with amino acids.
It is an object of the instant invention to provide a diester tocopherol derivative. In preferred aspects the instant invention provides tocopherol derivatives of high potency and of water solubility. Advantageously, in another preferred aspect the instant invention provides a water soluble tocopherol derivative of high potency wherein the compound includes the choline, vitamin B.sub.4 unit. A further object of the instant invention is to provide water soluble tocopherol derivatives which can further be used in applications in the fields of: medication, foods, cosmetics, fisheries, and animal husbandry. Other objects will become apparent as this description proceeds.